Mark Kaplan takes various (unnamed) people to task for claiming a lineage between the traditional left and Enlightenment values. He argues that Marx and the tradition that came down from him did not uncritically salute these values; they criticized them 'in their own name', exposing the way in which claims to universality at an abstract, theoretical level, and also at the formal level of civil and political equality, concealed a rather less rosy picture in the real world of economic and social differences, of exploitation and differential life advantages.
In arguing this Mark is, of course, quite right. It is easy to find textual support for what he says - ample textual support. What he will have more difficulty in establishing, however, is that the man who looked forward to a world in which 'the free development of each is the condition for the free development of all' may not quite properly be said to belong within the tradition of Enlightenment values; or that his criticism of these values in their own name was not, at least in part, a result of that fact. Mark imputes a number of dubious motives (again, to unnamed people) for so connecting Marx and the traditional left with the Enlightenment: those who do this apparently want to elide the difference between liberalism and the left - so as 'to meet the demands of present agendas'. What to say?
First, anyone's view of the differences, and the similarities, between liberalism and the left can be stated as and when the need arises. Second, there are other and worse types of outlook than liberalism which people on the left can get to lose a sense of difference with.